Yeah I remember reading about this, hence why I immediately noticed it was branded IBM on the face plate and thought it was cool and added bit of historical value to it ![Cool 8)](https://www.eevblog.com/forum/Smileys/default/cool.gif)
As for voltages yeah but I don't find obvious test points for them. Am trying to download the manual from Tekwiki but the download keeps failing ! Driving me nuts. So in the meantime I am doing it impro style, just looking around.
I noticed on a small board atop the main transformer, a dodgy looking axial electrolytic cap. Some nasty looking substance escaped from it, see picture...
I pulled it and measured it. Somehow capacitance and even ESR were still fine ! I replaced it anyway just to see if it would make any difference at all.
It's a 3uF 150V one. Plenty of 3,3uF but all low voltage. Closed I had with a high voltage rating was a 4,7uF 150V. Good enough for testing purposes I thought. So I soldered that in. Made no difference. Oh well...
......snip......
Now if I could bloody manage to download this freaking service manual !!!!! ![Rant :rant:](https://www.eevblog.com/forum/Smileys/default/rant.gif)
That capacitor is a Sprague 109D wet tant
they are well known for leaking the acidic electrolyte, following failure of the seal.
Oh, those again ?! ![ThumbsDown :--](https://www.eevblog.com/forum/Smileys/default/icon_thumbsdown.gif)
I remember you telling me about these things, when I showed the two crusty one in the trigger rotactor in my HP 120B scope !
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1222432)
No, those in the hp 120B are not tants, the pair of crusty capacitors in series on the trigger switch (205, C206) are ordinary aluminium electrolytics, part no. 0180-0050, my dead-tree edition manual says they are 40uF but disagrees on the voltage rating on different pages, one states 500V & the another 50V.
The 120B unreadable-crap-editionᵀᴹ manual from Agilent only has 500V mentioned (no separate page for list of hp parts numbers). Don't suppose someone could clean off the originals and confirm which voltage rating is correct. ![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif)
Looking at your picture, I'm doubting they are 500V due to the size, they don't look big enough and other manuals such as the 3400A list 0180-0050 as 50V.
David
OK !
50V or 500V yeah not quite the same thing !
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
However when you look at the schematic, 500V is silly. Plus, given the size of these caps and their capacitance value, 50V adds up, 500V would defy the laws of physics of cap technology of the day !
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
Well even today it would still be a tight fit...
So as Cubdriver jsut said, of course they are 50V...
Anyway, have some news for the 453. Bad new, as I though the CRT transformer is toast. Actually it smells like toast as well ! Hoping the smell will go away if I open the windows.... but it's midnight and chilly outside here...
I removed the back cover of the cabinet, hoping to find some CRT related componentry hiding there. I was well inspired, components there were.
See the CRT schematic attached. The primary winding of the transformer is fed via 18V unreg or so, switched by a big TO3 NPN tranny, Q930. Supply is protected by a 2A fuse. So not the most complex thing to figure out eh ? Fuse was blown... great. checked if the tranny was short collect / emitter... Was not. Checked the winding of the transformer.... shorted !
In case it was a red herring of some sort, misprobing or getting confused one way or another... I decided to give it a chance. No, I didn't replace the fuse hoping for the best, please !
![ThumbsDown :--](https://www.eevblog.com/forum/Smileys/default/icon_thumbsdown.gif)
No, I hooked my lab power supply again, so I can watch current draw... thing was clearly shorted, it would take as much current as I would give it. I stopped before the fuse rating (2A). Think I went up to 1.5A briefly, then I heard some faint and spurious noise coming from the scope... turned it off and pulled the plug. It was the CRT transformer.. thing was smelling hot, and a horrible chemical like smell was coming from it. What ever that was.
So clearly the primary was shorted, and blew the fuse.
So unless someone has a cheap spare transformer, this scope is toast and just taking up space.... don't have the equipment to rewind it and never done it so not an option. That said since it's dead, I have technically nothing to lose, can't get worse, so might as well pull it and unwind it ?! As good a pretext as any to get some hands on experience ?!
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif)
I don't know...
Well I am lygin, I have already unwound a transformer... the one from the SMPS of my Tek 2232 scope. MOSFET got shorted and 240V mains blew the primary of the coil/transformer of the pre-regulator... I remember taking notes of number of turns, wire disaster and resistance. It's all there on EEVBLOG in the appropriate repair thread, somewhere... was a few year ago.
Anyway, at any rate there is no quick fix so I can button it up and put it in storage mode to free the bench.
Would still love to fix it somehow, and see a trace on the CRT. Just for smiles.